Fireplaces, Heating Stoves, Flues and Chimneys - Stone around Fireplace/Hearth

hello,
I am in the early stages of putting ledgestone around a recent 3 way fireplace i had installed. I have a couple of questions concerning it.

1. The frame the firplace sits on is 18" above the floor. it was farmed flush to the outside dimensions of the fireplace. I need to extnd this farming out slightly to hold the 9" depth hearth i want to incllude around it. My question is, does one normally place the hearth stone so it looks as though the fireplace sits on it so flush with the bottom of the unit, or can i place it so the stone buts up against the fireplace slightly?

2. Has anyone purchased stone from one of the big box stores. I have a Lowes, Home Depot and Menards in my area?

3. Finally, when I spoke to the big box stores they said they boxes contained 8 linear feet( for corners). The specialty stone shop i went to did some sort of .75 multiplication to some number to determine the linear feet. If I have 120 inches of corne needed, is that 10 linear feet wherever i go, or what was this .75 thing they did at the specialy shop?

Thanks for all of the help.

Check the manufacturer's installation instructions for the fireplace, typically a 36 inch peninsular wood burning fireplace will require a 16 inch extension under the three sides below the firebox opening and 8 inches at the fourth side,

http://paragoninspects.com/images/sfba/hearthmantel/hearthextension3sideddiagra.jpg


If you have that extension at the floor you can place a secondary extension at the level of the firebox provided that it meets all the other manufacturers requirements for a hearth extension, however if you don't have the extension at the floor the manufacturer requires the full 16 inches at the elevated "hearth extension" at the firebox, for example here's a non-compliant peninsular fireplace at a recent home inspection:

http://paragoninspects.com/images/sfba/hearthmantel/hearthextensionundersized2s.jpg

and here's the logic behind the requirement: keeping hot embers off combustible materials and furnishings:

http://paragoninspects.com/images/sfba/hearthmantel/hearthextensionunderside3si.jpg

Thanks for the reply. I should have specified in my original post but maybe this doesn't make a difference. The Fireplace I had installed was a gas fireplace. Do the same requirements you sent still hold true?

Generally no hearth extension required for a manufactured gas fireplace:

http://heatilator.com/downloads/productPhotos/largeImages/gbfl.jpg

The logic is that you will not have hot embers rolling out of a gas fireplace.

Typically, the only exterior restrictions (as opposed to required clearance within the chase) for a manufactured gas peninsular fireplace are to adjacent walls or other combustibles (typically 36") and to mantels and their supports above. (Check the manufacturer's installations instructions, the vertical clearance depends on the mantle's projection).

Also, many manufactured gas peninsular fireplaces require clearance (typically 3.5") to combustibles at the blank end of the firebox assembly, generally there will be supplied metal spacer brackets to maintain this clearance and secure the firebox assembly.

Many gas fireplaces have louvers, vents or access panels near the base, you are not allowed to cover these.

Also, if you intend to use a floating hearth extension be mindful not to place heat sensitive objects such as candles on it.

wheeww...good to hear there are no requirements there. how about best practices? I do have the vent things you referenced on the bottom of the unit, but there is a solid metal support that runs the length of the unit that is probably an inch thick and the vents sits on that.

Any idea on the other 2 questions by chance or since they are more stone related, is there a better forum to post them that you know?

Thanks again for the help.